A specialist left-handed batsman and part-time medium pace bowler, Ranatunga's career with the Sri Lankan national team began in 1982, when Sri Lanka were relative newcomers to international cricket and was a key player in the team. Under Ranatunga's captaincy, Sri Lanka started to improve rapidly. Their growing success rate culminated with a dominating performance and triumphed in the 1996 Cricket World Cup. Although some of his actions caused some controversy, Ranatunga was praised for his leadership in raising a team long regarded as underdogs to the status of world champions.

A left-handed batsman and useful right arm medium pace bowler, Ranatunga made his first-class debut in 1981 at the age of eighteen and a year later played in Sri Lanka's inaugural Test match. In this match he became the first Sri Lankan to score a Test half century.

Ranatunga went on to captain Sri Lanka in 1988, taking control of the national team for the next 11 years, transforming it from a weak, routinely defeated team into a competitive and successful unit. He led the team to their greatest cricketing triumph, 1996 World Cup. His innovative captaincy took a Sri Lanka team, given little chance prior to the competition, for cricket's greatest prize. His strategies was commended by many cricketing greats and followed by other teams. He was the brain behind the strategy of scoring as many runs as possible in the first 15 overs of an ODI match in which there are field restrictions. This strategy was perfectly executed by Sanath Jayasuriya. This strategy was still followed by the batsmen in the Powerplays. He was widely recognised as a belligerent leader and was famous for defending his players at all costs regardless of what they did.[4]

The Sri Lankan national team were considered perpetual underdogs but this image changed completely during the 1996 Cricket World Cup, when Sri Lanka defeated tournament favourites Australia to win it under the captaincy of Ranatunga. This victory, for which Ranatunga was a pivotal part both as batsman and captain, started a new era of Sri Lankan competitiveness on the global stage; they had previously never passed the group stage of a world cup.

Ranatunga's weight was also notable for being considered excessive for a professional athlete. It gave rise to an incident during a game played in humid conditions when he called for a runner, claiming that he had "sprained something"; opposition (Australian) wicket-keeper Ian Healy responded with an insulting comment, falling under what is categorized in cricket as a "sledge", which was picked up by the stump microphones and broadcast live on television. Ranatunga was known for controversially calling a runner during long innings due to his level of fitness. After the second final of the One Day triangular series in Australia in the 1995/6 season, when the incident with Healy occurred, Ranatunga instructed his players not to shake the Australian players' hands. During this match, Sanath Jayasuriya and Australian paceman Glenn McGrath were also involved in physical jostling; Jayasuriya accused McGrath of racially abusing him, a claim that the bowler denied.[6]

Ranatunga is also remembered for his stand in a One Day International against England. Australian Umpire Ross Emerson called Muttiah Muralitharan for throwing. (Muralitharan was subsequently cleared by bio-mechanical experts hired by the ICC.[7]) Ranatunga exchanged heated words with umpire Emerson and led his team to a point just inside the boundary line, halting play and giving the impression that he was about to forfeit the match, until the Sri Lankan management conferred with him and play resumed. English captain, Alec Stewart, was openly critical of Ranatunga's behaviour. In a comment caught on the stump microphone he was heard to say to Ranatunga "Your conduct today has been appalling for a country's captain". The match was bad-tempered, with instances of shoulder-bumping.[8]

He is noted also for his repeated intense criticism of the Australian team, especially his long-standing rivalry with Shane Warne. During the 1996 World Cup, Ranatunga claimed that Warne was overrated, and during the final, Warne misexecuted a flipper, which turned into a full toss. Ranatunga pulled it over the boundary for the six and then stuck his tongue out at Warne. During the 1999 World Cup, Warne wrote a column calling Ranatunga a "disgrace". The Sri Lankan shot back by referring to his country's cultural heritage and then mocking Australia over convict settlement.

In 2005, Warne mocked Ranatunga's rotund figure, which had become more ample since his retirement, suggesting that he had swallowed a sheep.

There has always been between Warne and Ranatunga a grudging mutual admiration. When the former visited Sri Lanka in the aftermath of the 2004 tsunami to aid Muralitharan in his "great work"[9] there, he developed an amiable rapport with his long-time foe: "We even wagged," he confirmed later.[9] Not long after, however, Ranatunga was lambasting him in a scathing newspaper attack.

"You can't be mates with everyone," Warne wrote in his 2008 book Shane Warne's Century, serialised by The Times in September, "and if there was any way I could knock him down to number 101[10] for the purposes of this book, I'd be delighted to do so. But having taken on the task, I want to do it seriously, and the fact is that Ranatunga helped to put Sri Lanka on the cricket map. And you know what? Deep down, I'll quietly admit that I rated him as a cricketer."[9]